Hydrometallurgical treatment of nickel,cobalt and copper containing materials

ABSTRACT

A PROCESS FOR THE RECOVERY BY LEACHING OF NICKEL, COBALT AND COPPER USING SULPHURIC ACID AND EMPLOYING AGENTS CAPABLE OF INTRODUCING ALKALI METAL ION OR AMMONIUM ION TO THE PULP WHEREBY THE DISSOLUTION OF DESIRED METALS IS CONTROLLED AND THE IRON CONTENT OF THE SOLUTION IS REDUCED TO A LOW LEVEL. THE LEACHING MAY BE CARRIED OUT AT TEMPERATURES AND PRESSURES BELOW OR ABOVE ATMOSPHEERIC PRESSURE AND THE ATMOSPHERIC BOILING POINT OF THE PULP.

United States Patent 3,793,430 HY DROMETALLURGICAL TREATMENT OF NICKEL,COBALT AND COPPER CONTAIN- ING MATERIALS David Weston, 34 Parkwood Ave.,Toronto, Ontario, Canada No Drawing. Continuation-impart of applicationSer. No. 260,991, June 8, 1972, which is a continuation-in-part ofapplication Ser. No. 221,437, Jan. 27, 1972, which in turn is acontinuation-in-part of application Ser. No. 869,376, Oct. 24, 1969, nowabandoned. This application May 31, 1973, Ser. No. 365,626

Int. Cl. C22b 3/00 US. Cl. 42336 18 Claims ABSTRACT OF THE DISCLOSURE Aprocess for the recovery by leaching of nickel, cobalt and copper usingsulphuric acid and employing agents capable of introducing alkali metalion or ammonium ion to the pulp whereby the dissolution of desiredmetals is controlled and the iron content of the solution is reduced toa low level. The leaching may be carried out at temperatures andpressures below or above atmospheric pressure and the atmosphericboiling point of the pulp.

This application is a continuation-in-part of my prior application Ser.No. 260,991 filed June 8, 1972 which was a continuation-in-part of myapplication Ser. No. 221,437, filed I an. 27, 1972 which was acontinuation of application Ser. No. 869,376, filed Oct. 24, 1969, nowabandoned.

THE BACKGROUND OF THE INVENTION This invention relates to thehydrometallurgical treatment of materials for the recovery of nickel,cobalt and copper. Materials susceptible to treatment according to theinvention include nickel bearing laterite ores, nickel and copperbearing sea-nodule deposits, nickel or copper mineral treated productssuch as concentrated nickel or copper ores and other ores or smelter androaster products where nickel, cobalt or copper or any combination ofthese minerals or products are associated with iron and are susceptibleto leaching with sulphuric acid, and material from tailings dumps whichcontain residual quantities of copper.

Attempts to recover nickel and cobalt from the nickel laterities byhydrometallurgical processes such as leaching have been hindered by thepresence in the laterites of a substantial amount of iron mineral suchas geothite and hematite together with complex host rock iron minerals.When subjected to a sulphuric acid leaching, for example, part of theiron readily goes into solution where it has the eifect firstly ofcausing excessive sulphuric acid consumption and secondly of preventingmore than a certain proportion of the nickel and cobalt present fromgoing into solution. Once the iron is in solution it is very difficultand costly to separate the nickel and cobalt from the iron. Thissituation has resulted in commercial exploitation of the nickellaterites being generally confined to the production of ferro-nickel andin the use of pyrometallurgy and other expensive treatment steps incombinations with hydrometallurgy to reduce the iron content to anacceptably low value in the final ferro-nickel product. These processesgenerally employ complex flow sheets which are expensive to operate andrequire a high capital cost outlay.

SUMMARY OF THE INVENTION I have now found that it is possible, byproperly controlling conditions and the addition of certain reagents, toconduct a leaching process in which the nickel and cobalt areeflectively dissolved while the iron is prevented from 3,793,430Patented Feb. 19, 1974 remaining in the solution, whereby a pregnantliquor is produced containing a high proportion of the cobalt and nickelpresent in the original lateritic ore and with a nickel to iron ratiodown to as low as 50 nickel to 1 iron, from which pregnant liquor thecobalt and nickel are readily recoverable by known processing methodsincluding, for instance, ion exchange. I have further found that suchleaching techniques apply equally well to the recovery of copper andnickel values in a variety of materials from which such values werethought to be economically unrecoverable because of low grade, thepresence of sulphuric acid soluble iron, and the supposed insolubilityof the mineral values and the like.

According to my invention the laterite nickel ore or other material iscomminuted to a suitable degree of fineness for leaching which willgenerally be from a 28 mesh grind to about 90% minus 325 mesh and formedinto a pulp of suitable consistency which would normally be as high assolids as can effectively be handled during the cominution stage. Wherea dispersing agent is employed during comminution this pulp density maybe as high as 60% by weight solids whereas without a dispersing agent itmay be necessary to go as low as 25% by weight solids. The pulp is thensubjected to a first leaching stage with the addition of sufficientsulphuric acid to bring the pH down to a value below about 1.5 andpreferably below about 0.7 and the leaching is allowed to proceed atatmospheric pressure and temperatures varying from C. to the boilingpoint of the pulp, or if desired, and pressure equipment is economicallyjustified at higher temperatures and pressures. This leaching stage ispermitted to continue until there is a substantial concentration of ironin the solution. For instance, at a pulp density of 45% by weight solidsmy preferred concentration of iron is approximately 25 grams per litreof solution, which point is generally reached, in leaching carried outbelow the atmospheric boiling point, after a period of approximately 16hours. It will be appreciated that the laterites vary over a wide rangein both their iron and rock content. For instance, the normal variationin the laterites is approximately 10% by weight iron to a maximum of 45%by weight iron. The optimum conditions of my leaching process willtherefore change, within limits, depending upon the chemical compositionof the laterite being treated. When the above condition has beenreached, I then add to the pulp a precipitating agent for the iron instage additions during the remainder of the leach, in quantitiessufiicient to cause controlled precipitation of the iron from thesolution. When I use sodium chloride, potassium chloride, or a mixtureof the two salts, I prefer to add all of these salts prior to or at thestart of the leaching process. As precipitating agents I may use anyagent capable of introducing alkali metal or ammonium ions to the pulp.My preferred agents are potassium carbonate, sodium carbonate, sodiumchloride and potassium chloride. While potassium carbonate appears to bethe most effective, it is relatively high in price compared to sodiumcarbonate and this in many cases indicates the use of the latter foreconomic reasons. Similarly, potassium chloride is more expensive thansodium chloride, although more effective. While the indications are thatall alkali metals will produce the precipitation phenomenon, I excludefrom consideration rubidium and caesium on obvious economic grounds. Imay also use sodium sulphate, potassium nitrate or combinations of thesereagents with sodium or potassium carbonate and chloride. It isbeneficial in some cases to carry out the leach in the presence of anoxidizing agent which may also act as a precipitating agent.

Generally speaking, for a particular process the choice of precipitatingagent will be governed by economic factors. For instance, where thetreating plant is located near the ocean, in certain applications I mayuse sea water for the formation of my pulp and eliminate or reducematerially the amount of sodium or potassium carbonate or chloride. Thisis particularly true in the treatment of sea nodules containing copperand nickel.

The leach is continued until the desired economic level of solution ofmetal values has been attained and at this point if the iron content ofthe solution is not at a usefully low level, further precipitating agentis added to complete the precipitation and bring the iron content of thesolution down to the desired level.

While I have indicated that the purpose of my initial stage of leachingis to bring a desired amount of iron into solution and that the additionof the precipitating agent for iron usually follows this first stage, Ihave found that with the slower acting of the precipitating agents, suchas sodium chloride, sodium sulphate and the like, the addition of all ora certain quantity of these reagents during the comminuting process, orprior to sulphuric acid addition, will not prevent the concentration ofiron in solution from reaching a desired level for optimurn nickel andcobalt iron dissolution and I prefer in many cases I to make suchadditions during the comminution of theore in order to decrease theamount of relatively more expensive, faster acting precipitating agentswhich may beadded at subsequent stages of leaching. Further, smallincrements of the precipitating agent or agents may be added either tothe grinding stage or during the primary leaching stage.

As it is desirable to work at as high pulp density as possible in orderto control the sulphuric acid consumption and minimize plant size. Iprefer to carry out the comminution with the addition of a dispersingagent or a wetting agent or both. Among the available dispersing agents,I prefer sodium silicate because of its ready availability andrelatively low cost. Any wetting agent which is a powerful lowerer ofsurface tension and has low frothing characteristics is suitable.

The leach described generally above may be modified if desired by theintroduction of various gaseous media. For instance, I have found thatthe introduction of sulphur dioxide accelerates both the iron and cobaltdissolution. Carbon dioxide on the other hand retards iron and cobaltdissolution and accelerates nickel dissolution. The introduction of airaccelerates iron dissolution, retards iron deposition and cobalt andnickel dissolution. Thus, while the introduction of gaseous media to theleach is not an essential feature of my process, in certain instancesuseful additional control of the process maybe achieved with possiblysome saving in operational :costs, due to shortened time or reduction inacid consumption. This will be particularly true of carbon dioxide wherewaste combustion gases could be beneficially introduced into the leach.

If as a precipitating agent a strong oxidizing agent such as potassiumdichromate is employed, the rate of deposition of iron is stronglyaccelerated.

It is important that the rate of deposition of the iron be such that theconcentration of iron in the solution does not drop below a certainvalue until the dissolution of nickel and cobalt has approached itsdesired end point since it appears that the dissolution rate of nickeland cobalt is adversely aifected if the amount of iron in solution fallsbelow about 1 gram per liter. However, the optimum balance between therate of iron deposition and the dissolution rate for cobalt and nickelwill depend upon the composition of the ore being treated and will varybetween laterites of diiferent chemical composition. The results which Ihave achieved on the laboratory scale indicate that by using the processof the present invention recoveries of higher than 80% of the nickel andcobalt may be obtained in the pregnant solution concurrently with thefinal pregnant solution containing littlemore than a trace of iron.

.Myinvention also comprehends the carrying out of the process attemperatures above the atmospheric boiling point of the pulp inasmuch asthe chemical phenomena associated with dissolution of the desiredmineral values follow the same pattern at higher temperatures andpressures and the normal acceleration of the dissolution rate associatedwith rises in temperature applies. Thus, although the use of hightemperatures and pressures involves the use of costly pressure equipmentand places physical limitations on the manipulative procedures involved,the resulting shorteningof total leaching-time to obtain a desireddegree of dissolution and the fact that a coarser grind may be toleratedmay economically outweigh the disadvantages of having to employ pressureequipment. In cases where the higher temperature and pressures arejustified it is an advantageous feature of the invention that the finaldeposition of iron may be carried out at atmospheric pressure after thedesired degree of dissolution of metal values has been achieved at thehigher temperatures and pressures.

EXAMPLES OF THE OPERATION OF THE INVENTION The following examplesillustrate the invention. In all of the examples except as otherwisenoted the same apparatus was employed which consisted of alaboratoryball mill for comminuting the ores, a constant temperaturethermostatically controlled oil bath equipped with approximately 2 litersealable glass pots equipped with motor driven stirring devices and twopH meters equipped with special electrodes for accurate high temperaturelow pH readings. Samplings were taken by means of 50 and- 25 cc.pipettes at prescribed intervals. The progress of cobalt and nickeldissolution was followed by analyzing the solids for undissolved cobaltand nickel. Iron in solution and the final cobalt and nickel in solutionwas determined by standard quantitative analysis. All manipulativeprocedures were standardized throughout.

EXAMPLE I A sample of Penarroya New Caledonia lateritic nickel ore hadthe following head analysis:

535 grams of this ore (estimated 515 to 520 grams dry) were ground for15 minutes in the laboratoryball mill at a pulp density of 30% by weightsolids, with the addition of 10 cc. of 1% solution of a wetting agent (atrimethyl nonyl ether of polyethylene glycol) and 16 grams of sodiumsilicate. The resulting pulp was transferred to a testing pot on the oilbath at approximately C. and conditioned for 20 hours at which time theaddition of cc. of 10% by weight C.P. sulphuric acid reduced the pH ofthe pulp to 0.8. The conditioning was continued for 20 hours, a samplewas taken for analysis and 15 grams of dry crystalline potassiumcarbonate was added to the pulp. An additional quantity of 5 grams ofpotassium carbonate was added every two hours until a 'total of 30 gramshad been added. 20 hours after the first addition of potassiumcarbonate, a second sample was taken for analysis 15 grams of potassiumcarbonate were added and each two hours thereafter, an additional 5grams of potassium carbonate were added until the total addition forthis stage had reached 30 grams. 24hours after the second addition ofpotassium carbonate was commenced, a sample was taken for analysis andsamples were taken at 24 hour intervals thereafter.

The following were the metallurgical results:

Percent by weight Pregnant solution Ni (in Co (in Fe, solids) solids)gms/l.

1 cc. (3.1. HzSOi were added after sample was taken.

A 835 gram sample of the same ore as that used in Example I was groundfor minutes in a laboratory ball mill at a pulp density of approximately50% by weight solids in the absence of any reagents following which theresulting pulp was transferred to a testing pot on the oil bath where200 cc. of C.P. sulphuric acid were added to reduce the pH of the pulpto 0.7. A temperature of approximately 90 C. was maintained and the pulpwas conditioned for 20 hours at which time a sample was withdrawn foranalysis. Six liters of air per hour were then introduced to the pulpand the conditioning was continued for 20 hours at the end of which timea sample was taken for analysis, following which the air was turned oifand 25 grams of dry crystalline sodium sulphate were added to the pulpfollowed by a further 25 grams three hours later. Twentyhours after thefirst addition of sodium sulphate a sample was taken for analysis and25grams of sodiumv sulphate were added followed four hours later by afurther 25 grams. The conditioning was continued for 24 hours when asample was taken for analysis. After a final conditioning period ofanother 24 hours, a further sample was taken for analysis.

The following were the metallurgical results:

Percent by in eight Pregnant solution Ni (in Co (in Fe, Ni,

solids) solids) gins/1. gmsjl. pH

These results indicate the accelerating effect of the introduction ofair upon the solution rate of iron and also indicate that the action ofsodium sulphate as a deposition agent is relatively mild compared tothat of potassium carbonate as indicated in Example I.

EXAMPLE III A further sample of 835 grams of the same ore as that usedin Examples I and II was ground for 15 minutes in a laboratory ball millat a pulp density of approximately 25% by weight solids in the absenceof any reagents following which the resulting pulp was transferred to atesting pot on the oil bath at a temperature of approximately 90 C. and120 grams of sodium chloride was added following which the pulp wasconditioned for 24 hours and a sample was taken for analysis. After afurther period of conditioning for 20 hours a second sample was takenfor analysis and 225 cc. of GP. sulphuric acid was added andconditioning was continued for a further 20 hours and a further samplewas taken for analysis. 25 grams of dry crystalline potassium carbonatewere then added to the pulp and conditioning was continued for 24 hourswhen a sample was taken for analysis. After a further 24 hours ofconditioning, the final sample was taken for analysis. The metallurgicalresults were as follows:

Percent by weight Pregnant solution Ni (in Co (in Fe, Ni,

solids) solids) gms./l. gms./l. pH

A 540 gram sample of lateritic nickel ore supplied by the InternationalNickel Company of Canada, and having a head analysis of 1.42% by weightnickel, 0.126% by weight cobalt and 42.2% by weight iron, was ground ina laboratory ball mill at a pulp density of approximately 30% by weightsolids in the presence of 75 grams of sodium chloride. The resultingpulp was transferred to a testing pot on the oil bath at a temperatureof approximately 90 C. and the pulp was conditioned for 2 hours at whichtime 150 cc. of CF. sulphuric acid were added and the pulp Wasconditioned for a period of 20 hours following which a sample was takenfor analysis and the pulp was conditioned for a further 20 hoursfollowing which a further sample was taken for analysis. Five grams ofpotassium carbonate were added to the pulp and the pulp was conditionedfor a further 20 hours when a further sample was taken for analysis and11 grams of potassium carbonate were added to the pulp. After 24 hoursof further conditioning a further sample was taken for analysis and 4grams of potassium carbonate were added to the pulp and the pulp wasconditioned for a further 24 hours before a final sample was taken foranalysis. The metallurgical results were as follows:

Percent by weight Pregnant solution Ni (in Co (in Fe, Ni, SOlldS)solids) g'ms./l. gms./l. pH

These results indicate that sodium chloride is effective as a depositionagent and when followed with relatively small stage additions ofpotassium carbonate results in a very elfectiveq combination of irondeposition and nickel and cobalt dissolution.

EXAMPLE V 870 grams of a sample of lateritic ore supplied by theInternational Nickel Company of Canada and having a head analysis of1.42% by weight nickel, 0.126% by weight cobalt and 42.2% by weightiron, was ground for 25 minutes in a laboratory ball mill at a pulpdensity of 45% by weight solids in the presence of 32 grams of sodiumsilicate. The pulp was transferred to a testing pot on the oil bath at atemperature of approximately 90 C. and after 4 hours conditioning, gramsof sodium chloride were added and the pulp was further conditioned for20 hours. 225 cc. of CF. sulphuric acid was added, condi-. tioning wascontinued for 20 hours and a sample was taken for analysis. 10 grams ofpotassium carbonate was added Percent by eight; Pregnant solution Ni (inCo (in Fe, Ni,

solids) solids) gmsJl. gms./l.

This test shows the effectiveness of the combination of sodium silicateand salt followed by relatively small additions of potassium carbonatein stages.

EXAMPLE VI Another 870 gram sample of the same ore used in Example V wasground in a laboratory ball mill for 25 minutes at a pulp density of 45%by weight solids in the presence of 32 grams of sodium silicate. Thepulp was then transferred to a testing pot on the oil bath at atemperature of approximately 90 C. and after 4 hours conditioning 120grams of sodium chloride were added and the pulp was further conditionedfor a period of 20 hours. 225 cc. of C.P. sulphuric acid were added andthe conditioning was continued for 20 hours and a sample was taken foranalysis. grams of crystalline sodium sulphate were added and theconditioning was continued for a further 20 hours and a sample was takenfor analysis. A second quantity of 10 grams of sodium sulphate wereadded and the conditioning was continued for 24 analysis. A further 12.5grams of potassium nitrate were added, the pulp sample was taken foranalysis after 24 hours and after continuing with the conditioning for afurther 24 hours a final sample was taken for analysis.

Percent by weight. Pregnant solution N1 (in Co (in Fe, Ni,

solids) solids) gms./l. gmsJl. pH

This test indicates the ability of potassium nitrate to act as adeposition agent in the process of the invention.

' EXAMPLE VI'II A11 835 gram sample of the ore used in Example I wasground for 25 minutes in the laboratory ball mill at a pulp density ofapproximately 50% by weight solids and the pulp was transferred to atesting pot on the oil bath at a temperature of approximately 90 C., 200cc. of C.P. sulphuric acid were added and the pulp was conditioned for20 hours and a sample was taken for analysis. 25 grams of potassiumcarbonate were then added followed by a further 25 grams 4 hours later.20 hours after the first addition of potassium carbonate, a sample wastaken for analysis and the pulp was conditioned a further 20 hours, asample was taken for analysis and 25 grams of potassium dichromate wereadded followed 4 hours later by 25 grams of potassium carbonate. Anextra sample was taken for analysis 3 hours following the addition ofthe potassium dichromate. Conditioning was continued and a sample wastaken for analysis at 24 hour intervals, with 25 cc. of C.P. sulphuricacid added after the last addition of potassium carbonate.

The metallurgical results were as follows:

hours and a further sample was taken for analysis. A Percent by weightPregnant solution further addition of 6 grams of sodium sulphate wasmade,

N1 on Co (in Fe, Ni, the conditioning was continued a further 24 hoursand solids) solids) gins-ll. gmsJl. pH a sample was taken for analysis.

The metallurgical results were as follows: 1.08 0.070 V 0.57 0. 034

regnant solution 0' 47 0. 032 Ni 00 "Fe, Ni, 0.33 0.031 (in solids) (insolids) gms.l1. gms./1. 0. 34 0.028

Tune, 1115 20 0.62 0. 043 6.58 0.75 The fore oing results illustrate theaccelerating effect 333333333: 8:23 8:833 53513333333333 i133 50 thatPotassium dichromate has 113011 the deposition of 3s 0. 40 0. 027 1. 200. s7 1. 35 iron where the iron in solution fell from 0.92 to 0.20 gramThis test shows the eifectiveness of sodium sulphate as a depositionagent permitting good dissolution of the cobalt and nickel whilebringing the iron in solution down to an acceptable level. Repetitionsof the same procedure employing ammonium carbonate in the one case andlithium carbonate in another case indicated that these two compounds actas deposition agents in substantially the same manner as sodiumsulphate.

EXAMPLE VII 540 grams of the same ore as that employed in Examples V andVI were ground for 15 minutes in the laboratory ball mill at 30% byweight solids following which the pulp was transferred to a testing poton the oil bath at a temperature of approximately 90 C., 150 cc. of C.P.sulphuric acid were added and the pulp was conditioned for a period of20 hours following which a sample was taken for anaylses. 12.5 grams ofpotassium nitrate were added, the conditioning was continued for 20hours and a further sample was taken for analysis. A further quantity of12.5 grams of potassium nitrate were added to the pulp, conditioning wascontinued for a further 20 hours and a further sample was taken for perliter in the first 3 hours following the first addition of potassiumdichromate.

EXAMPLE 1X agent (a trimethyl nonyl ether of polyethylene glycol) and 20grams of sodium carbonate. The pulp was then transferred to a testingpot on the oil bath at approximately C. and conditioned for 4 hours whencc. of C.P. sulphuric acid were added together with 10 grams of sodiumcarbonate. The pulp was conditioned for 16 hours, a sample was taken foranalysis and 5 grams of sodium carbon-ate were added. Conditioning wascontinued for 12 hours and a sample was taken for analysis and 50 gramsof sodiumcarbonate were added. Conditioning'was continued and sampleswere taken for analysis every 12 hours. In this example, the ironcontent of the solids was determined by chemical analysis.

The metallurgical results were as follows:

Percent by weight Pregnant solution Ni (in Co (in Fe (in Fe, gms./

solids) solids) solids) 1. pH

The above results indicate the action of sodium carbonate as an irondeposition agent and show the course of the leach with a relatively lowquantity of sulphuric acid.

While the invention has been illustrated in the foregoing examples asapplied to the treatment of nickel bearing laterite ores, it is obviousthat it applies equally as well to beneficiated nickel bearing lateriteores and other Ni bearing ores or beneficiated ores or smelter orrosater products where the nickel is associated with iron andsusceptible to leaching with sulphuric acid (herein referred to asnickel mineral treated products).

EXAMPLE X This example illustrates the effect of using increased amountsof sodium chloride in the initial leach liquor.

Following the same procedure as in the preceding examples with alateritic nickel ore having a head value of 0.70% nickel and 0.089%cobalt and using a leaching temperature of 95 to 98 C., periodic samplesof the liquor and residue were taken and analyzed to indicate theprogress of the leach.

The results were as follows:

10 chloride not only is there an increase in nickel and cobalt insolution, but also the added effect of precipitation of iron that hasgone into solution.

Particularly noteworthy in the solution analyses is the apparentdifferential elfect on the iron precipitation which occurs withincreasing amounts of sodium chloride.

EXAMPLE XI This example shows the eifect on pressure leaching usingsodium chloride and sulphuric acid at in excess of 100 C. In this casethree tests were run at a temperature of 200 C. in a laboratory pressureleaching apparatus wherein the natural presssure developed at thistemperature was about 275 p.s.i.g. Using the same amount of sodiumchloride in each test, that is, 50 lbs. per ton, and varying the acidinput from 313 lbs. per ton in the first test to 628 lbs. per ton in thesecond test, and 1027 lbs. per ton in the third test, at the end of 24hours leaching time under these conditions the percentage of the nickelin solution using 313 lbs. of sulphrric acid per ton of solids was andthe cobalt, 78 a.

At 628 lbs. sulphuric acid per ton and at 24 hours leaching time, thenickel in solution was 85% and the cobalt, 92%. In using 1027 lbs.sulphuric acid per ton, at the end of the 24 hour period the nickel insolution was 96%, and the cobalt, 93- /z%.

In using the pressure leaching instead of atmospheric pressure, I preferto add additional precipitation salts such as sodium carbonate andpotassium carbonate to the pulp and condition at atmospheric pressure ata temperature of from about C. to the atmospheric boiling point of thepulp for a minimum period of 8 hours.

Residue analysis Leach test number 14 15 16 17 18 19 20 Lbs. NaCl perton ore 15 30 45 90 100 After 18 hrs., percent:

Ni 0. 43 0. 41 0. 38 0. 45 0. 38 0. 37 0. 37 Co 0. 031 0. 030 0. 027 0.026 0. 027 0. 028 0. 027 After 42 hrs., percent:

Nl 0. 385 0. 335 0. 305 0. 275 0. 280 0. 275 0. 295 C0 0. 031 0. 030 0.027 0.025 0. 206 0. 025 0. 0235 After 66 hrs, percent:

62. 9 65. 7 70. 0 74. 2 75. 7 77. 1 78. 6 75.3 75. 3 82. 0 80. 9 88. 886. 5 86. 5 Heads, percent:

Ni 0.70 On 0. 089

the

the

EXAMPLE XII In this example an old plant copper tailings were used inexactly the same equipment and under the same con- Solution analysesLeach test number 14 15 16 17 18 19 20 This table shows the etfect ofthe use of sodium chloride with sulphuric acid at a temperature of about95 ditions as in Example X. The head value was 0.33% total copper, and0.25% copper as shown to be acid soluble C. wherein with the use ofincreasing amounts of sodium 75 in sulphuric acid alone by the standardmethod of 11 analysisflhe folowing test is the optimized of the series.This optimized test was run under the following conditions:

Pulp temperature 70 C. 7

Sodium chloride 20 1bs. per ton. Sulphuric acid "addition 45 lbs. perton.

At the end of 8 hours leaching time, the final tailings analyzed 0.22%total copper, showing outstanding dissolution is not only the acidsoluble copper, but also of the original copper content that was notacid soluble in the use of sulphuric acid alone. It was found that theminimum temperature for acceptable dissolution of the copper mineralswas 50 C.

EXAMPLE XIII The following three series of tests were carried out on thetailings from an old copper plant flotation circuit. Conventionalleaching tests gave poor metallurgical results with recoveries in therange of 50-55% of the contained copper values. The chemical analysis ofthesetailing was 0.33% total copper, and 0.24% acid soluble .copper. Thesulphide copper is taken as the difierence Pounds per ton copper placedsodium silicate: in solution 0.0 75.6 1.0 79.0 2.0 81.0

The graphed metallurgy showed that the optimum'of' sodium silicate was3.5 lbs. per ton with 82.8% of the total copper in solution. Thus, inusing a dispersion agent.

prior to the leaching cycle, the amount is reasonably critical andshould be controlled within narrow limits for optimum results.

Where the optimum amount of sodium silicate is used as a dispersant inthe presence of a suflicient sodium ion the increase in recovery isoutstanding, as is indicated in the Series II test which follows. Insome applications where suflicient sodium ion is present by virtue ofthe It will be noted that in using sodium chloride to increase thesodium ion concentration extraction is improved. y

In using sodium chloride in combination with a dispersant as above, theminimum amount for optimum 'metallurgy'has been found to be 6.0 lbs.perton'."

The minimum temperature foracceptable leaching time cycles is 50 C. Noupper limit of temperature has been determined. This tempearture will bea function of leaching time and at temperatures in excess of about 100C. will of necessity be inenclosed vessels, and develop various naturalpressures, dependent on the-ultimate temperature used.

In this series of tests the copper in solution varied from 2.0 to 2.2grams per liter, and iron from 1.5 to 1.7 grams per liter. v a

, 1 Series III In this series of tests varying amounts of sodium chlo-.ride alone were used as the sodium ion producing agent. The conditionsof all tests were, using 45 lbs. per ton of H 80 temperature of 70 C and6 hours, leaching time cycle.

Pounds per ton Percent of total copper sodium chloride placed insolution It will be noted that the break in the recovery curve takesplace on the addition of between .10 to 15 lbs. per ton of NaCL A t 30lbs. of NaCl per ton the tailings analyzed 0.037% total copper and0.008% acid soluble copper, leaving 0.029% as presumably sulphidecopper.

' As the headscontained 0.09% acidsoluble copper, the

dissolution of the sulphide copper can probably be .;attributed to thecombination of the sodium ion and oxidation of these old plant tailingsin the tailings dump.

In other applications. where valua ble sulphide minerals are present,and where 'preoxidation has not takenplaq use of the optimum amount ofsodium silicateas a-dispersant it may be economically desirable simplyto predisperse the material to be treated and then to leach with.

the addition of acid only. I I

Series .II

This series of tests combines both the predispersion of the pulp withsodium silicate, and increasing the concentration of sodium ion presentby the addition of sod ium chloride in various amounts. All of thefollowing tests were carried out using 4.0 lbs. per ton sodium silicate,

52 lbs. per ton H 50 a temperature of C., and 'a leaching cycle of 6hours. 1

The sodium chloride was varied from 4.0 lbs. to 12.0

lbs. per ton.

Percent of total Pounds per ton copper placed sodium chloride:

in solution 4 88.6 6 ;,-90.0 8 90.5 10 91.2 12 91.2

phides.

the use ofoxidizing agents such asoxygen, potassium dichromate, andpotassium perchlorate, either prior to or during the leach may assistthe dissolution of the sul- While the invention has been illustrated inExamples 'XII and XIIIasapplicable to old plant copper tailings it 'isobvious that it applies generally to copper and copper nickel materialsand tailings where the copper and nickel are associated with iron andsusceptible to leaching'with sulphuricacid;

The following series of examples were'tests carried out on a. lateriticnickel bearing ore high inmagnesia content. In the examples where thetemperature was suificiently high for the pulp to boil, the individual.test .pots were equipped with water-cooled condensers that returned thecondensate *directly to itsindividual 'potr used as 1n the previousexamples.

The .same thermostatically controlled leach bath was The ore sample wasdried at 110 1, crushed to rninus inch, and SOD-gram charges ground in alaboratory rod mill at 45% solids.

The fineness of the grind was to minus 35 mesh. i

Following the grind the pulp was transferred from the rod mill to theindividual leaching pot at a density f of about 40% solids.

'In each case either a wetting agent, and upto 4 lbs. per ton of solidsof sulphuric acid was added toj the rod ro t e sulphuric-acid alone, toimprovethe flow- ..ability of thepulp, I

d In addition, by lowering the theipulp during grinding to below apH of7.0, there isa surprising bene- 13 ficial eflect on the thickeningcharacteristics of the pulp. This can be a most important factor inplant practice where following grinding of the ore to the suitabledegree 1 for eifective leaching, the pulp may be thickened and thedensity to leaching controlled at the desired percent solids. Mypreferred pH range in the grinding circuit is about 4.0 to 7.0. If thepH is too acidic the steel grinding media and mill liner consumptionwill increase apprecileaching at temperatures lower than'thatmosphericboiling point of the pulp, in order to hold maintenance of the equipmentat a reasonable level. 7

It will be appreciated that a small percentage of the ticularly if thepH is maintained below about 5.0. The

following was the head analysis of the sample tested in all of thefollowing examples.

Percent by weight Lbs./ton solids solution to less than 0.1 gram perliter is between 80 to 100 lbs. KClper ton of ore. V The lateriticnickel bearing ores have a wide variance I in chemical composition. Forinstance, the iron content nickel may go into solution during itspreparation, par- Co 0.08 Fe 18.8 MgO 14.9 SiO 39.6 A1 0 2.83 C1203 LoI9.7

Reagent Tri-methyl nonyl polyethylene glycol ether (TNPGE) 0.01 H SOLeach temperature, 90 C.

The following table shows the reagents to the leach and themetallurgical results obtained. In each test "the potassium chloride(KCl) and sodium chloride (NaCl) varies from about 8% to o Similarly,there is a large variance in silica, alumina, and magnesia content.

For this reason, in using my process wherein the optimum sodium ion isused alone, or potassium ion alone, or a combination of the two, andwherein my economic preferred salts are sodium and potassium chloride tosupply these ions, their optimum quantities may vary considerably. Thefollowing table shows the minimum and maximum quantities when usedalone.

Lbs. per ton are when used alone NaCl K01 Min. Max. Min. Max.

My preferred range in using NaCl in combination with KCl is about to 200lbs. NaCl per ton solids, and about 10 to 160 lbs. KCl per ton solids.

. In treating nickel bearing manganese-iron sea deposit nodules the sameminimums apply in using NaCl or KCl alone, or in combination. Themaximums, to obtain optimum economic recovery, are lower.

Where I use sea water as part or all of the make-up solution I prefer toadjust the pulp density to the major economic point making the maximumuse of the contained NaCl. For instance, if I require 200 lbs. NaCl perton solids, and I use sea water containing lbs. NaCl per ton of seawater, I would use 3 tons of sea water to one ton of solids, resultingin 180 lbs. of NaCl per ton solids.

v o .To raise the NaCl content to 200 lbs. NaCl per ton solids, 5.0; '40

it would also be necessary to add 20 lbs. NaCl per ton solids.

. Such a mixture would be 25% solids, which density is were added priorto the sulphuric acid. In each test 990 Sample assays Solutions, Lbs/tonSograms/litre 1idS,-'.- DH at NaCl K01 Ni N1 Fe 01 20 hrs.

Test Number: I i q 1 1 Calculated.

I the recovery of the nickel and cobalt from solution, where it isnecessary to reduce the chromebe'low 0.1 'grar'n'p'er liter it will benecessary to raise the KCl ratio to Na'Cl.

Where KCl is used alone, as the KCl is raised in quantity not only isthere a marked increase in nickel recovery,

butalso a marked decrease of both'iron and chrome in.

solution. The break in the curve reducing-the chrome in in the lower endof the range for effective leaching in my process taking intoconsideration heat requirements and size of leaching tanks required.

My preferred pulp density range is 25 to 60% solids.

EXAMPLE XV The following series of tests shows the comparative'metallurgy using NaCl alone, KCl alone, combined NaCl fand KCl, and theeffect of the introduction of ferric ions into the pulp.

In all of the tests 1080 lbs. H 80 was added to the pulp at thebeginning of the leach and following the addition of the salts. Thetemperature of the leach was C.

and the pulp was sampled at 20.5, 45 and 67.5 hours after the sulphuricacid addition. For comparative purposes the 67.5 hour sample only isshown.

- Sample assays V Los/ton Solutions 'r Ferric Solids. pH at No; NaCl K01oxide N1 Ni Fe 67.5 hrs.

1501 11.; noted that using KCl alone, not only is the nickel. in thesolids the lowest, but also the iron in solu- 70 J v In the use of asmall quantity of ferric oxide, that is,

ti 'oifisnig lowest.

only 1,85 lbs. per ton of solids, a most surprising effect is thereduction of iron in solution.

Its comparative test is 42. This elfect of the ferric ion is notunderstood.

. tion in 17 hours leaching time.

termine the ultimate possible recovery.

1 5 EXAMPLE XVI In the following series of tests the leachipots wereequipped with condensers to return] condensate vto the individual leachpots. The temperature of theoil bath was Where pressure leaching is usedin the first stage, following the pressure leach I prefer to condition;the .pulp

for a minimum period of 8 hours .at atmospheric pressure andtemperatures below the boiling point of the pulp in the presence ofsufiicient quantity of at least one salt selected from the group of NaCland KCl. I prefer to have at least the major part of the salt presentduring the pressure leaching stage.

In all of the tests, with the exception of Test 65, 140 lbs. of NaCl and40 lbs. of KCl per ton of ore respectively were added to, the pulpfollowing grinding and prior to the initial H SO addition. In Test 65 nosalt addition was made to the pulp.

Sample assays Lbs/ton H 80 Solutions, Solids grams/litre pH Test AfterTime,

number Imtial 20 hrs. hrs. Ni Co Ni Fe Time pH 17 1. 37 5. 4 2. 4 17 3.4 6 590 590 41 0. 17 0. 006 11. 3 6. 7 44 1. a 100 0. 10 11. 9 4. 100 1.75 17 1. 16 6.0 3. 8 17 3. 25 61 660 520 41 0. 13 0.005 10.8 8. 6 44 1-1 100 0. 08 12.0 6. 3 100 1. 75 17 0.82 7. 8 4. 8 17 2.5 6 790 390 410.14 0. 005 10. 7 7. 5 44 v 1.3 r 100 0. 09 11. 3 4. 9 100 1. 8 17 0.708. 1 5. 3 17 2. 1 64 860 320 41 0. 14 0. 005 13. 6 9. 6 44 1. 2 100 0.10 14. 6 6. 7 100 1. 9 17 0. 74 8. 6 34. 8 20 1. 45 65 1 1,128 41 0.630.010 7.8 30. 5 44 1.35 100 0.63 8.9 30. 2 100 3.0 17 0.24 10.0 7. 720 1. 5 6 1, 8 41 0. 20 0.005 9. 5 5. 9 44 1. 65 100 0. 15 10. 8 3. 9100 2. 05 17 0. 24 12. 6 8. 5 20 1. 55 68.. 3 1, 128 41 0.20 0.006 15. 98. 8 44 1. 70 100 0. 16 15. 2 4. 2 100 1. 9 17 0. 23 11.2 7. 5 20 1. 5569 3 1, 128 41 0. 20 0. 006 11. 6 6. 9 44 1. 65 100 0. 145 12. 1 3. 7100 1. 65

i 1 riii i "f it o1 i C n a it on 0 a and KCl, 6.25 lbs. of ferrous sulhate was added to the 111 rim to the'HzS 0 4 addition. p P p p a dd 0N801 and K01, 6.25 lbs. of ferric chloride wasadded to the pulp prior tothe B2804 addition.

105 C. depending on the salt concentration used and the altitude. i Inthe first series of tests the sulphuric acid'was stageadded and the pHof the pulp lowered tobelow 1 '.5'with sulphuric acid on the secondaddition following" 20 hours leaching time.

Where the leaching of nickel and cobalt values is carried out attemperatures in the range of 70 C. to the atmospheric boilingtemperature of the pulp, or'alternately, under pressure from theatmospheric boiling point to higher temperatures under pressure, Iprefer touse a minimum time period of 8 hours for further leachingfollowing the lowering of the pH of the pulp below 1.5' with sulphuricacid.

L In the second series of tests the NaCl were added to the pulp prior tothe sulphuricacimand the sulphuric acid added in a single stage'at thebeginningjof the leach. i i

' I ri conditionin g the leach under atmosphefi'pistire and in'theboiling temperature range of the pulp, the rapid dissolution of. thenickel values are-shown inTest 66 where in excess'of 90%" of the nickelvalues were placed in's'olu- The leaching time was carried out to 100hours to de- In using temperatures higher than the/boiling pointe of thepulp and with at least part of the leach carried out under pressure therate of leaching time may be appreciably reduced, and in some'cases,even though maintenance becomes a major factor, can be economicallyjustified. v f i In such cases a maximum temperature of.about200 C.

than about 24 hours.

tion of Na or K ion, it will be noted that in Test 65 the I 1Incomparing the results of Tests 65 and 66 where all leachc'onditions'were the same with the exception that Test 66 had present inthe pulp 140 lbs. of NaCl and lbs. KCl per ton respectively, while Test65 had no addivunleached Ni remaining in the solids was 0.63% as against0.15% in Test 66, indicating thatthe Na and K ion are not only acting asan efiective agent for the iron precipitation butalsoas'a dissolutionagent for the nickel and cobalt.

The cobalt tailing in Test 65 was 100% higher than in Test 66 and thefinal Fe in solution in Test 65 was approximately750% higher than inTest as.

A surprising result from this series of tests was the ing temperaturerange of the pulp. It will be noted that in Tests 66 to 68 inclusive, inexcess of 90% of the nickel values'were, placed in solution in 17 hoursleach time.

tion of temperature, economically, it is doubtful that tem- Wherecomparatively low pressure leaches are used and temperatures in therange of about 95 to 200 C., the I leaching time for dissolution of aminimum of 90% of the nickel values would be less than 12 hours. Themaximum pressure at 200 C. would be about 275 p.s.i.g.

As the rate of dissolution of the nickel will be a funcperatures inexcess of about 300 C. could be justified, as the major portion of thenickel would be in solution in less than about 4 hours. For the combinedleaching of the nickel and cobalt values and acceptable precipitation ofthe iron in solution, the minimum time of the process is With copperbearing materials the minimum time period of the process is about 2hours, and the maximum about 48 hours.

It will be appreciated that the pregnant solution containing the nickeland cobalt values may be separated from the impoverished solids byconventional methods such as filtration, and recovered by well knownprocesses such as hydrogen sulphide precipitation of the nickel.

I claim:

1. A hydrometallurgical process for the leaching of at least one mineralfrom the group of minerals consisting of nickel, cobalt and copper, andfrom the group of materials consisting of lateritic nickel and cobaltbearing ores, sea deposit nodules containing nickel and copper minerals,copper ores containing sulphuric acid soluble copper minerals, andflotation plant tailings containing sulphuric acid soluble copperminerals comprising; forming a pulp of the said material at a pulpdensity of from about 25 to 60% solids and wherein the said material isin the fineness range of from about 28 mesh to about 90% minus 325 mesh;reducing the pH of the said pulp to below 1.5 with at least onesulphuric acid addition; conditioning said pulp in a temperature rangeof from about 50 C. to 300 C. in the presence of at least one ironprecipitating agent selected from the group of agents consisting ofsodium chloride and potassium chloride and wherein the said agent hasbeen added to the pulp in sufficient quantity to cause substantinalprecipitation of iron in solution concurrently with dissolution of thesaid nickel, cobalt and copper minerals, and wherein said conditioningis carried out for a sufiicient period of time whereby to produce apregnant solution enriched in said mineral values and low in ironcontent and a solids tailings product impoverished in said mineralvalues.

2. A hydrometallurgical process for the leaching of sulphuric acidsoluble copper minerals from the group of materials consisting of copperores, copper mineral treated products and flotation plant tailingscomprising: forming a pulp of the said material at a pulp density offrom about 25 to 60% solids and wherein the said material is in thefineness range of about 28 mesh to about 90% minus 325 mesh; reducingthe pH of the said pulp to below 1.5 with at least one sulphuric acidaddition; conditioning said pulp in a temperature range of 50 C. to 300C. in the presence of at least one iron precipitating agent selectedfrom the group of agents consisting of, sodium chloride and potassiumchloride and wherein the said agent has been added to the pulp insufiicient quantity to cause substantial precipitation of iron insolution concurrently with dissolution of said copper values and whereinsaid conditioning is carried out for a sufiicient period of time wherebyto produce a pregnant solution enriched in said copper values and low iniron content, and a solids tailings product impoverished in said coppervalues.

3. The process of claim 2 wherein the said temperature range is fromabout 50 C. to 105 C.

4. The process of claim 2. wherein at least one of the said ironprecipitating agents is potassium chloride.

5. The process of claim 2 wherein prior to reducing the pH of the saidpulp to below 1.5 the solids in the said pulp are dispersed with theaddition of a dispersing agent.

6. The process of claim 2 wherein the said precipitating agent is sodiumchloride.

7. The process of claim 2 wherein the said iron precipitating agent issodium chloride and wherein the amount added to the said pulp is in therange of from about 4 lbs. to about 30 lbs. per ton of solids.

8. A hydrometallurgical process for the leaching of nickel minerals fromthe group of ores consisting of laterites and manganese-iron sea depositnodules comprising: comminuting the ore in a wet grinding circuit to afineness in the range of from about 28 mesh to about minus 325 mesh;subsequently forming a suspension of the said comminuted ore at a pulpdensity in the range of from about 25 to 60% solids; reducing the pH ofthe said pulp to below 1.5 with at least one sulphuric acid addition;conditioning said pulp in a temperature range of from about 70 C. toabout 300 C. in the presence of at least one iron precipitating agentselected from the group of agents consisting of sodium chloride andpotassium chloride and wherein the said iron precipitating agent hasbeen added to the pulp in suificient quantity to cause substantialprecipitation of the iron in solution concurrently with dissolution ofthe said nickel minerals and wherein said conditioning is carried outfor a sufficient period of time whereby top roduce a pregnant solutionenriched in nickel values and low in iron content, and a solids tailingsproduct impoverished in nickel values.

9. The process of claim 8 wherein during said comminution the pH of thepulp has been lowered with sulphuric acid to within the pH range ofabout 4.0 to 7.0.

10. The process of claim 8 wherein the said temperature of the said pulpduring the leach is in the range of from about C. to about C.

11. The process of claim 8 wherein at least one of the said ironprecipitating and nickel dissolution agents is sodium chloride andwherein the said agent has been selected from the group consisting ofsodium chloride and sea water and wherein the amount added to the saidpulp is in the range of from about 50 lbs. to about 350 lbs. per ton ofsolids.

12. The process of claim 8 wherein the said sufiicient period of time isin the range of from about 8 hours to hours.

13. The process of claim 8 wherein at least one of the said ironprecipitating and nickel dissolution agents is potassium chloride andwherein the amount added to the said pulp is in the range of from about10 lbs. to about 200 lbs. per ton of solids.

14. The process of claim 8 wherein during at least part of the leachcarbon dioxide is fed into the said pulp.

15. The process of claim 14 wherein the said carbon dioxide is a wastecombustion gas.

16. The process of claim 8 wherein ferric chloride is present in thepulp during at least part of the leach.

17. The process of claim 16 wherein a minimum of 5.0 lbs. per ton of thesaid ferric chloride has been added to the pulp.

18. The process of claim 8 wherein at least part of the said leachingprocess is carried out in the temperature range of about 95 C. to 200 C.and under a maximum pressure of about 275 p.s.i.g.

References Cited UNITED STATES PATENTS 913,708 3/1909 Dow et al 423- X1,193,734 8/1916 Sulman et al. 75-115 X 2,719,082 9/ 1955 Sproule et al.75-119 X 2,754,174 7/1956 Roberts 423-140 X 2,831,751 4/ 1958 Birner423-140 3,130,043 4/ 1964 Lichty 423-140 X 3,434,947 3/1969 Steintveit423-140 X 3,367,740 2/ 1968 Zubryckyj et al 423- 3,466,144 9/ 1969 Kay423-150 X 3,637,371 1/ 1972 Mackin et al. 75-101 R HERBERT T. CARTER,Primary Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 793,430 Dated February 19 41974 David Weston Inventor(s) It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

The term of this patent subsequent to Feb. 19, 1991, has beendisclaimed.

Signed and sealed this 1st day 0;? April 1975.

(SEAL) Attest:

C. MARS-HALL DANI-I RUTH C. MASON Commissioner of Patents attestingOfficer and Trademarks FORM PO-1050 (10- COMM-Dc 376m ".5. GOVERNMENTPRINTING OFFICE: B69 930

